Conventionally, a LOC (Lead-On-Chip) semiconductor package includes a semiconductor chip encapsulated by an encapsulant to prevent the contaminations of dust particles and moisture and a plurality of leads of a leadframe carrying the chip and transmitting the electrical signals of the chip to external electrical components. “Lead-On-Chip” means the leads of the leadframe are extended to the active surface of a chip with the chip attached to the leads of a leadframe to eliminate or minimize die pad(s). Since the CTE of the leadframe is different from the one of the chip, the thermal stresses induced by the thermal cycles during die-attaching processes and molding processes will be concentrated at certain leads, especially at the leads adjacent to the chip edges, leading to delamination or broken leads.
As shown in FIG. 1, a conventional LOC semiconductor package 100 comprises a plurality of leads 110 of a leadframe, a die-attaching layer 130, a chip 140, a plurality of bonding wires 150, and an encapsulant 160. As shown in FIG. 2, each lead 110 has a bonding finger 111. The leads 110 are arranged at two corresponding longer sides of a leadframe with a fan-in design toward the center of the packaging area to make the bonding fingers 111 in linear arrangements with fine pitches. As shown in FIG. 1 again, the chip 140 has an active surface 141 with a plurality of bonding pads 142 formed on the active surface 141 where the leads 110 are attached to the active surface 141 of the chip 140 by a die-attaching layer 130. The bonding wires 150 electrically connect the bonding pads 142 to the bonding fingers 111. The encapsulant 160 encapsulates parts of the leads 110 including the bonding fingers 111, the die-attaching layer 130, the chip 140, and the bonding wires 150. However, as shown in FIG. 2 and FIG. 3, several bonding fingers 111A located at two sides of the disposition area of the bonding fingers 111 will experience the largest stresses, leading to easy delamination between the bonding fingers 111A and the chip 140, or between the bonding fingers 111A and the encapsulant 160. Moreover, the delaminated bonding fingers 111A even contact with the adjacent bonding fingers 111 during molding processes leading to electrically short.